Method of aerial transportation



Jan. 3, 1928. 1,6555113 N. TESLA METHOD OF AERIAL TRANSPORTATION Filed Sept. 9. 1921 J 11 9 6 6 I .Z 2 Q @j Z 2: g 7 O P a o 0'- T 8 A I d 1 6 a 7 c? o 9 4 10 JO 1 11 o a z Jl/VVENTOR BY mm A TTORNLYQE' Patented 3, 1928' T D STATES PATENT, OFFICE.

' mx'ona TESLA, on NEW YORK, N. Y.

METHOD OF AERIAL TRANSPORTATION.

- Application filed September 9, 1921, Serial No. 499,519, and in Great Britain Aprihl, 1921.

The utility of the aeroplane as'a means of transport is materially lessened and its commercial introduction greatly hampered ow-.

ing to the inherent inability of the mechanism to readily rise and alight, which is an unavoidable consequence of the fact that the required lifting force can only be produced by a more or less rapid translatory movementof the planes or foils. ,In actual experience the minimum speed for ascension and landing is a considerable fraction of that in full flight, and the principles of design do not admit of a very great advance in this respect without sacrifice "of some desirable feature. For this reason planes of i very large area, high lift wing-sections, de-

flectors of'the slip-stream of thepropeller, or analogous means, which might be helpful in these operations, do not afford the remedy sought. This indispensable high velocity, imperilling life and'property, makes it necessary to equip the machine with special appliances and provide suitable facilities at the terminals of the route, all ofwhich en'- tail numerous drawbacks and difficulties of a serious nature. 80 imperative has it become to devise some. plan of doing away with .these limitations of the aeroplane that the consensus of expert opinion charactcrizes the problem as one of the most pressmg and important and its practical solution is eagerly awaited by those engaged in the development of the art, as well as the general public.

-Many attempts have been made to this end, mostly based on the. use of independout devices;f0r the express purpose of facilitating and insuring the start andfinish of journey, but the operativeness of the arrangements roposed is not conclusively demonstrate and, besides, they are yet. beenachieved. EvinnderStanding of the subject.

The prospects of a flying machine of this kind appear at first attractive, primarily beto the inadequacy of the' an elucidation of. I WhlCh is deemed necessary for the clear.

cause it makes possible the'carrylng of great loads with a relatively small expenditure of energy.- This follows directly from the fundamental laws of fluid propulsion, laid down by W. "T. M. Rankine more than fifty years ago, in conformity with'which the thrust is equal to the integral-sum of the products of the masses and velocities of the projected airparticles; symbolically expressed, I

T=Z(mv)'.

air set in motion is E=zG m= a great thrust can be obtained with a comparatively small amount of power simply by increasing the aggregate mass of the particles and reducing their velocities. Tak ng a special case for illustration, if .under given conditions be ten pounds per horse-power, then a hundredfold increase of the mass of air, accompanied by a reduction of its eflective velocity to one-tenth, would produce a force of one hundred pounds per horsepower. But the seemingly great gain thus secured is of little significance in aviation, for the reason that a high speed of the thrust I On the other hand, the kinetic energy of the objectionable, constructively or otherwise, to

suchan extent that builders of commercial apparatus-have so far not considered them of. sufficient value to den I'Itfrom present practice.

More recently, professional attention has been turned to the helicopter which is devoid of planes as distinct organs of support and, presumably, enablesboth vertical and horizontal propulsion to be satisfactorily accom plished througly the instrumentality of the propeller: alone. However, although this idea is quite oldand-not a few-e erts have endeavored to carry it out in various ways,

: travelis generally an essential requirement. which can not be fulfilled except by propelling the air at high velocity, and

' that obviously implies a relatively small thrust.

, Another quality commonly attributed to the helicopter isgreat stability, this being,

a -pare'ntly, a logical inference judging from tli e location of the centers of gravity and pressure. It will be found, though, that contrary to this prevailing opinion the device, whilemoving. n any direction other than up or down,- is in an equilibrium easily disturbed and has, moreover, .a pronounced tendencyto oscillate. It is true,-ef course, that when the axis of the propeller 1s vertical and the'ambient air quiescent the machine is stable to a degree, but if it is tilted even slightly, or if the medium becomes agitated, such is no longer the case. In'explanation of this-and other peculi- ]arities, assume thehelicoptr poised in still air at a certain height, the axial thrust T justequalling the weight, and let the axis of the propeller be inclined to form an angle a with the horizontal. The change to the new d, the Corresponding 26700 eet the height of the un form atmosphone, then as a-consequence and at the same time I horizontal thrust position will have. a twofold effect: The vertl08 .l thrust-will be diminished to ITV.=T Sill oz, I F I there will be produced a Un der the action of the unbalanced force of gravity the machine will new fall along a Y curve toa level below and if the inclination of the propeller" as well as its speed of rota ti'on, remain unaltered duringthe descent, the forces T, T,. and T will continuously increase in proportion to the density of the air until the vertical component T,, of the axial thrust T becomes equal to thegravitational attraction; Theextent of the drop be governed the inclinatio'npf the propeller axis and fora givenangle it will 'be, theoretically, the same no matter at what altitude the events take place. To getanidea of. its magnitude suppose the elevations of the .upperand lower strata measured from sealevelbe it, andjn, respectively, (Z, and, air-densities and H= of Boyles law sa d the relation will exist in orderft'hat the vertical colnponent hf the axial thrust in the lower stratum should support the weight. .Hence .M-h',='26700 l0g, i i-54"";= 3346mm In reality the drop will be much greater L pl a a 1 alllag r" Taking, in a special casegjthe angle a=" then V v and for the machine, upon reaching the lower layer with a high velocity relative t9 the described become rectilinear.

. over, -t

. more, the vertical sustaining effort of the repeller will correspondingly diminish an the inedium, will .be urged further downalong the curvedpath and the kinetic energy, in

the vertical sense, possessed by the moving mass must be annihilated before :the fall is arrestedin a still denser" air stratum. .At this point thelupward thrust will be far in excess-0t the opposed pull of the weight and the apparatus will rise with first increasing and then diminishing speed to a height which may approximate the original.v From there to v it will again fall and so on, these'opera-tions being repeated during the forward flight, the up and down excursions from the main horizontal line gradually diminishing in magnitude, After a lapse of time, determined bynumerous influences, the excursions should cease altogether-and the path But this is next to impossible as-canbe readily shown by pointing out another curious feature of the helicopter. l I i In the foregoing the axis of the propeller was: supposed to move always parallel to itself, which result might. be accomplished gbythe use of an adjustable aileron. In this ronnection it may be pointed out, however, that such a device will not act in the manner of a rudder, coming into full playat intervals only'and per-forming its functions economically, but will steadily absorb energy,

motive power and adding another to the many disadvantages of the helicopter.

Let now the machine be possessed'of a certain degree of freedom, as will be the case normally," and observe-in .the first place that thus occasioning a considerable waste of the blades of.the propeller themselves con-.

,stitute planes developing a reaction thrust, the pressure on the lower leading blade being greater thanthat exerted on the higher 10118 7 owing to the compression of the .air by the body 0f. the machme and increased density in that region. This thrust, tending to diminish the angleu, will obviously very during one revolution,-being.maxim1nn in a position when the line of symmetr of the two propeller blades andthat of ight are in a vertical plane and right angles to it; Nevertheless, when-the hori- I zontalspeed is great it may be considerable the angle diminishes upto a maximum for As the axis is tilted more and machine will-fall. with a rapidly increasing velocity, ffinally exceeding the horizontal when the reaction of the blades be upward so as to increase-the angle a and thereby .cause the machine'tdsoarwhich may well be magnified to an extent such as to bring about a complete overturn and plunge to earth.

It held by someexperts that the helicopter, because of its smaller body resistance, would be capable of a higher speed thanthe aerophane; But this is an erroneous conclusion, contrary to the laws of propulsion. It must be borne in mind that in the former type, the motive power; being a greater mass of airmust be set in motion with a velocity smaller than in .the latter, consequently it must be inferior in speed. But even if the air Were propelled in the direction of the aXis of the screw with-thesame speed. V in both -of them, while the aeroplane can approximate the same, the helicopter could never exceed the horizontalcomponent V cos a. To be explicit, imagine that the air current flowing with the velocity along the propeller axis inclined to forman angle on with the horizontal, be .replaccd by two streams one vertical and the other hori zontal of velocitiesrespectively equal 'to V- sin 0: and V cos a, it will be evident that a; helicopter in its forward flight could only. approximate and never equal the speed V cos oz of the horizontal air current no matter how much 'the resistance be reduced for,

according to a-fundamental law of propulsion, the thrust would be -nil atthat velocity. The highest efiiciency should be obtained with the machine proceeding at the rate V cos a but the most economical utilization of power would be effected when oi= in which case the speeds of both the horizontal and. vertical streams will be 0.7 V. From this it may .be inferred that,

theoretically, the best performance mi 'ht be secured in propelling the helicopter ibrward. with .a speed more or less approxi but the resultslattained inpractice will be necessarily much inferior.

mating 0.35 V

because without special L as are herein set forth the device, as pointed out; above, would plunge down and shoot up in succession, at the same time executing provisions such smaller oscillations, which motions will motor,

retard its flight and consume a considerable portion ofthemotive energy all themore so asthe losses incident to the'controlling means will be correspondingly increased.

Another very serious defect of. this kind of flying machine, from the practical point of view, is found in its inability of supporting itself in the air inoase of failureofthe the projected area of the propeller blades being inadequate for reducing the speed of the fall sufliciently to avoid disas and this is an almost fatal impediment to its commercial use.

direction;

My invention meets .the' present necessityin a simple manner without radical departure in construction and sacrifice of valuable features'fincidentally securing advantages' which should prove very beneficialin the further development of the art. Broadly expressed, it consists in a .novel method of transportingbodies through the air according to which the machine is raised and lowered solely by the propeller and sustained in lateral flight by planes. To accomplish this a light andpowerful primemover is necessary and as particularlysuitcd for the purpose I employ, preferably, a turbine of the kind described Patent No. 1,061,206,- of May 6, 1913, which not only fulfills these requirements, but is especially adapted to operation at high temperature, A I also make arrangements whereby the flying machine. inatically or at will of'the operator, caused in my U. S...

may be, auto facts, which -are to'--function either as a helicopter or an aeroplane.

Full knowledge offthese improvements lustrates the machine in the. starting or landmg position and Fig. 2, in horizontal flight.

Fig. 3 is a plan view of the-same with the upper. plane partly lroken away.

. The structure is composed of two planes or foils 1, 1 rigidly joined. 'lheir length and anc'e apart may be such as to form a nearsquare for the sake of smallness and compactness. With the same object the tail is omitted or, if used,it is retractable. The motors 2, 2-in this case turbines of the kind described in my patent before referred to, and other 3 parts of the motive apparatus are placed with due regard to the centers of gravity and pressureand the usual controlling means are provided. In addition to these i any of the known stabilizing devices may be embodied in the machine. At rest the planes are vertical, or nearly so, and-likewise the shaftdriving the'propeller 3, which is 0011- struct'ed iof a strength, size and pitch that will enable it to raise theentir e weight with the motors runnin at an even greater rate than when prope ing the --m'achi ne horifrom the turbines through suitable gears. The seats 4, 4, l for and passengers are-suspended on trunnions 5, 5 on which they can turn through an angle of about 90, springs and cushions (not shown) being employed to insure and limit their motion through this angle. The usual devices for lateral and directional control, 6, 6 7, 7 and 8, 8 are prozontally. Power is transmitted-to the shaft the operator" I vided with mechanical connections enabling theioperator to actuate the devices by hand or foot fromhis seat inanyposition. -At the start, 'suflicientjpower' being. turned on by. suitable means, also within-his reach, the

.machine rises -vertically in the air to theas the angle ofinclina'tion diminishes and 'the speed in horizontal direction increases.

' 'From' the foregoing it will beunderstood that, simultaneouslywith the tilting of the machine, the operator will increase the i for the reduction of sustaining force which -f0llows inevitably'from the diminution of angle on and beiore. the reaction of the planes. can come into full eflect. He will thus prevent a downward plunge .and the production of dangerous oscillations which have been dwelt upon above, and by suitable manipulation of'the apparatus and giadual cutting down of the power developed by the prime mover, as forward velocity is gained and the" planes take up the load, he maycause themachine to advance horizontally along a sensibly straight .line, 'aaconditi'on e'sential to the attainment of the practical results. descending, the .forward speed is reduced and the machinerighted .agam, acting as'a helicopter with the proasthe '(levme s ,slowed down and righted causing the planes to lose part'or all of their sustaining 'efiorts, theoperator will apply:

I more power to the propeller' increasmg thereby the thrust to the required magnitude and in'all such operations of starting and I loading W ll as for e l ti height, meeting the air conditions orfor other liprposes it his-object to modify pr p led at a greatly increased 'specialimeansiof control may? propeller thrust: in about the'same meas 88 the Varyingreaction ofthe planesmayzdemand inorder that the lifting force be -sensibly -'constant. Evidently-also, when-- by the 'motors even though less eficiently thahunder their normal wor conditions. provided,

- if 11' ms: for the power supply extreme inthese'operations. Owmgtqits simplicity the notiye apparatus is very reli- .speedy and yet yery safe machine; for com-- thrust of the'propeller inorder to compense' mercial use. Especially good practical re- 1 peller supporting "all the load. 1 Obviously,

angle of the propeller axis to the horizontal,

planes have been proposed I able in operation, but should the power give out accidentall landing can still be easily eifect ed by v0 planing. For this purpose, inaddition to wheels 9, 9 and 10, 10 wheels 11,11 are employed, the latter being mounted on the forward endunder the lowerlplan'e and,so that when the machine rests on level ground the propeller shaft will have the desired inclination which is deemed best for rising in the mannerof an aeroplane. Such an aeroplane constructed and-operated as described, unites the advantages of both types and seems to meet best the require: ments of a small, compact, exceedingly sults are obtainable by the use f my turbine which can be depended upon to develop the can be conveniently attained by tempora-rily supplying more of the working fluid to the rotor and driving it faster, or running it at about the same 'speedand increasing the ef fort by adjustment of the pitch of the propeller, or other means known'in' the art.-

The latter should-be designed towvo'rkmost economically .dnring'the flight, as its efii- 'ciency in the starting and landing operations is of relati'velysinall importance. Instead of a single large screw as described a number of smaller ones-may be used, in which case gearingican be dispensed with. The biplane seemsto suited for the chief purpose and other.

machine, especially with large inclination to operate,

at which it is generally expected is ,quiteunsuitable for speedy aerial trans-- port; it is incapable'of proceeding horizon tally along a straight line under the prevailin'g air' con'ditions; it; subject to. dangerous plunges and oscillations and, what is most important from the commercial and practical point of view, it is almost certainly doomed. to destruction in case the motive power givesout; drawbacks and defects are overconie by the methods and apparatus I have described through which a' noveltype of flying machine may berealized 1 all the advantages of the helico ter being at the same time safe and capab of a speed equalto'or even greatly exceeding that-of the present aeroplane. I v To .my knowledge various forms of aero- 'with the ,object of attaining 1' results but a careful] study shows that none of them is capable the as thosehere contemplated for o Operation as well.

t ems want of methods iS-suitab apparatus.

104) contemplated but the invention-is applicable .to monoplanes 7 To sum up, the' helicopter type of flying means of which this method is or may be carried out either in the special form illus trated or in modifications of the same, as this is the subject of a separate application. What I desire to secure by Letters Patent 1s:

1. The hereinbefore described method of aeroplane transportation which consistsin developing by the propelling deviceayertical thrust in excess of the normal, .causing thereby the machine to rise in an approximately vertical direction, tilting it and simultaneously increasing the power of the motor and thereby the propeller thrust, then gradually reducing the power and thrust as forward speed is gained and the planes tak e up the load, thus maintaining the lifting force sensibly constant during flight, tilting the machine back to its original position and at the same time. increasing the power of the motor and thrust of the propeller and effecting a landing under the restraining action of'the same. I.

2. The method of operating a helicopter which consists in varying thepower of the a motor and thereby the thrust of the prope1- ler according to the changes of inclination of its axis, so as to maintain the lifting force sensibly constant during the forward flight.

3. The above described method of transporting from place to place a heavier than air flying machine, which consists in applying power to the propeller while its axis is in a Vertical position sufficient to cause the machine to rise, tilting it and at the same time applying more power to increase the thrust, then gradually diminishing the power as the load is transferred from the propeller to the planes, tilting back the machine and so controlling the applied power as to eflect a slow descent upon the landing place under the restraining action of the propeller.

4. In the transport of bodies by aeroplane, the method of controlling the propeller thrust and reaction of the planes by varying the power of the motor correspondingly with the inclination of the machine so as tomaintain the lifting force sensibly constant during the forward flight.

In testimony whereof I hereto aflix my signature.

NIKOLA TESLA. 

